The noun is derived from Middle English spavein, spaveine (“swelling on horse’s leg causing lameness; disease causing lameness in horses”), from Old French espavain, a variant of esparvain, esprevain, esprevin (modern French éparvin, épervin). The further etymology is unknown; one suggestion is that it is from Frankish *sparwan (“sparrow”), though this is seen as quite tenuous.
The verb is derived from the noun.